Diesel CGR process and structure

ABSTRACT

Disclosed is a manifold coupled to at least one cylinder of a diesel engine through at least one valve to pass or block gas flow between said manifold and said cylinder, with a specific list of restrictions imposed on said flow. Also, a manifold coupled to at least a pair of the cylinders of a multi-cylinder diesel engine through at least one valve to pass or block gas flow between said manifold and said cylinder, with the same restrictions imposed on said flow. The so formed structure is suitable to CGR.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Patent Application Ser. Nos. 61/400,704 of Aug. 2, 2010 and 61/404,169 of Sep. 29, 2010 and 61/404,346 of Oct. 4, 2010.

FIELD OF THE INVENTION

This invention relates to diesel engines and, more particularly, to processes and structures for improving the efficiency of the combustion cycle, reducing the harmful emissions of diesels and the electronic control of such processes.

BACKGROUND OF THE INVENTION

To improve emission at part load operation, exhaust gas recycling (EGR) is widely used in diesel engines. By definition, exhaust gas is the gas exhausted by the engine, upon exhaust valve opening, that is, during blow down. Prior to that event, and after the commencement of the compression ignition, the cylinder gas is still in its combustion and expansion phase. By half stroke of the expansion phase, over 90% of the combustibles are combusted, however. The pressure and temperature of the cylinder gas suddenly drops by 3-6 folds upon exhausting. Thus the combustion gas of a diesel engine has many times higher temperature and pressure than its exhaust gas.

EGR in diesels is done by two ways. Firstly, by residual gas entrapment resulted, when the cylinder is incompletely flushed by intake air. Secondly, by external redirection of some exhaust gas form the exhaust manifold into the intake manifold. The first may be assisted by turbocharger turbine back pressure and by intake gas throttling. The second, by supercharging assist.

By combustion dilution, EGR reduces NOx emission but increases the HC, CO and PM (hydrocarbon, carbon monoxide and particulate matter—mainly soot) emissions. However, it displaces fresh intake air and thereby reduces the oxygen available for combustion, thus it reduces engine power and torque. This way, EGR works against engine downsizing. To counterbalance that effect, the EGR is often cooled at further expense of engine performance.

Although skilled artisans have devoted considerable R&D toward the improvement of EGR systems by electronic controls, none could overcome the negative consequences of the intake air displacement problem, the major drawback of the EGR in diesels.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the diesel EGR intake air displacement problem by substituting or compounding the engine by a CGR (combustion gas recycling) process.

In the cylinders of a multi cylinder diesel engine, improvements therein according to the principle of the invention includes a manifold, which is pressurized by combusting, gas depleted from one cylinder of a multi cylinder diesel engine and—concurrently or sequentially—decompressed by depleting that manifold combustion gas—which may be still rich in combustibles—into the entrapped air of another cylinder of the same engine, as well as means to command such process by a CGR structure.

Unlike EGR, CGR does not displace intake air and, due to UHC and PM (unburned hydrocarbon and particulate matter or soot) as well as heat recycling, boosts engine performance by automatic HCCI (homogenous charge compression ignition) assist effect. The CGR rate can be higher than the EGR rate, resulting in cleaner emission. The CGR can be all times on at any engine load and speed.

It is another object of this invention to provide for partial CGR assist effect and for an all times on CGR process, which recycles heat.

It is yet another object of the present invention to provide for the electronic control of CGR and with that adjust engine performance or emission quality on demand by the operator or by the physical or logistical conditions.

It is yet another objective of this invention to provide for CGR of a single cylinder diesel engine as well.

It is yet another objective of the present invention to provide structures—including valves, leg pipes, manifolds or pressure tanks and a control system—for the CGR process.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings:

FIG. 1 is a pneumatic circuit diagram of a preferred embodiment of the invention, illustrating a CGR process.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

The above problems and others are at least partially solved and the above objects and others realized in diesel engines, when their EGR is substituted or supplemented by CGR or, when CGR is added to two or four stroke diesels lacking EGR.

According to the principle of the invention, the introduction of CGR is mainly practical in multi cylinder engines, using a small volume combustion gas manifold. However, it is also executable in single cylinder diesels with large manifold volume.

FIG. 1 illustrates a preferred embodiment of the invention by assembly 100, comprising structures and processes, which will be specified in their functional order as follows:

Air—which may contain some other gases—is sucked in into open ended intake manifold 1, and passes to air filter 2 for particulate matters and dust cleaning. Then it passes through cooler 3, which is equipped with coolant feed line 31 and return-line 32 of water or other suitable liquid or gas of sufficiently low temperature. The cooled air temperature is monitored by temperature sensor C3, which feeds signal to the engine's computer, which maintains the process control necessary for the proper operation of the engine and its supplemental CGR. The air then is sucked in by compressor 4, which boosts its pressure and thereby increases its mass flow rate. Compressor 4 is driven (powered) by drive D6 and speed controlled through controls receiving control signal C4 from said computer. Then, through intake valve 51, the chilled and compressed air, intermittently enters into upper cylinder (working) space 56 of diesel engine cylinder 5. Valve 51 is controlled by cam signal or action 51, which comes synchronized from engine crankshaft 58. Crankshaft 58 is monitored by said computer, though encoders signal C5. It may receive speed control signal as well (not shown). Drive D6 may come from turbine 6 or from crankshaft 58. These two cases correspond to turbocharging and supercharging processes respectively. FIG. 1, illustrates the turbocharging case. Space 56 is of a quasi harmonically variable volume space, supplemented by the volume of pressure vessel 10, which is dead space formed by the lag pipe connecting cylinder 5 and CGR valve 11. Into space 56, fuel 53 is injected intermittently, commanded by said computer through signal C53. In space 56, said fuel burns into combustion gas, which may contain some high temperature residual unburned fuel (a composite of hydrocarbons and carbon) and oxygen, under high pressure. Said combustion increases the pressure—by at least a magnitude—of space 56, which drives (powers) the engine, turning its crankshaft 58. In case valve 11 is a poppet valve, operating in the cylinder head, vessel 10 however is eliminated. In forward flow, space 56 intermittently receives CGR gas from vessel 12 through valve 11 and vessel 10. In reverse flow, vessel 12 intermittently receives gas from space 56 through valve 11 and vessel 10. In pipe 13, the CGR flows forward and reverse intermittently between cylinder 5 and one of the cylinders—otherwise identical to cylinder 5—of the same engine, sharing a common crankshaft 58. The CGR flows into space 56 only when pressure in space 56 is rising and at a higher level than the pressure level of vessel 12. The CGR flows out from space 56 only when pressure in space 56 is falling and at higher level than the pressure level of vessel 12. Thus the volume of space 56 pneumatically does not “see” the volume of vessel 12. The two actions, notably the CGR gas inflow and outflow to and from space 56, can however be consecutive, without any time separation. In such a case of operation, during the opening time of valve 14, first CGR gas flows into and then out of space 56 in such a way that the two actions are separated by the volumetric minimum of space 56. The CGR flow is further restricted by limitations imposed on the timing of valve 14, which includes the set time of valve opening and closing, in the following way: Valves 51 and 52 are closed during any CGR flow into or out of space 56. CGR inflow into space 56 may be early in the phase of pressure rising of space 56. That is called early inflow. CGR inflow out of space 56 may be early in the phase of pressure falling of space 56. That is called early outflow. CGR inflow into space 56 may be late in the phase of pressure rising of space 56. That is called late inflow. CGR inflow out of space 56 may be late in the phase of pressure falling of space 56. That is called late outflow. Early inflow may be followed by early outflow. Late outflow may be followed by late inflow. Late inflow may be followed by early inflow. However, very late outflow cannot be followed by very late inflow, while very late inflow can be followed by very early outflow. The end of the inflow can be inseparable from the beginning of the outflow; however the end of outflow cannot be inseparable from the inflow. These operational restrictions distinguish this diesel CGR process from internal EGR (exhaust gas recycling), surcharging by air or other gases and other diesel engine technology, which may alter the diesel gas cycle by any gas addition or removal into or out of the cylinder space. Valve 11 interrupts a pipeline, which connects vessel 10 to pressure vessel 12, which represents the volume of common rail (CR) pipe 13, which interconnects cylinder 5 with the rest of the cylinders of a multi-cylinder engine, which comprises cylinder 5. Pipe 13 however may be eliminated, in which case vessel 12 is to be retained. Said computer monitors the pressure of vessel 10 by signals pressure P10 and temperature C10, as well as oxygen (alpha) sensory signal (not shown separate). Valve 11 is a normally closed two-way electro-pneumatic valve, piloted alternatively by pressures P10 and P12 or by pressure P12 only or by external pressure (not labeled). The pilot lines are solenoid or piezo-electronic controlled by needle valves using control signal C5, directly from crankshaft 58 or processed by said computer. Valve 11 however can be cam operated poppet valve using signal-action C5, in which case vessel 10 and its monitoring (P10 and C10) is eliminated, or P10 and C10 becomes cylinder space 56 monitoring. Vessel 12 and pipe 13 may be configured to be a common structure, called CGR manifold or combustion gas manifold. The pipe, which connects vessel 10 to space 56, may be configured as a single structure, called leg-pipe. Such structures however may be formed by cavities formed in the cylinder head of cylinder 5. Vessel 12 is protected from overpressure through check valve 15 by the normally closed pressure relief valve 16, which vents overpressure through open end 17. Valve 16 is shown a passive spring loaded valve, which however can also be controlled by said computer, electronically and also can be eliminated, if overpressure protection is ensured otherwise. Valve 16 however can be eliminated, since valve 14 may also act as pressure relief valve or simply because pressure protection of vessel 12 is ensured by vessel sizing of vessel 12 and by the timing and operation of valve 14. Some service pressure, less than overpressure, is released from vessel 12 into catalytic converter 7 via commanded pressure relief line R17, which is passed by valve 14, which is piloted by pressure P12 and controlled by signal C12 coming from said computer, processed or direct. Such service process may be necessary for afterburning or heating up processes due in converter 7 or by pressure release purposes. Vessel 12 is also monitored by said computer via signals C12 and gauge pressure P12 or its corresponding pressure or temperature or oxygen contents, similarly to the monitoring of vessel 10. Open end 17 may however be directed to converter 7 or muffler 8. The lower cylinder space 57, the crank case) is vented trough open ended vent 59 and fed by oil line 54 and scavenged by oil line 55. However, the crank case oiling may not be pumped externally, but by the piston moving in cylinder 5. Crankshaft 58 gives control signals or actions C51 and C52 to command the intake and the exhaust processes of cylinder 5 respectively. Valves 51 and 52 are normally closed. Space 56 is intermittently vented through exhaust valve 52, which receives its control signal or action C52 from crankshaft 58. The gas leaving space 56 is called exhaust gas. Exhaust gas passes trough and powers turbine 6, which has an output drive D6, which is connected to compressor 4, powering it. Drive D6, however may be connected to a dynamo or other device to power other utility equipment. Leaving turbine 6, the exhaust gas pressurizes catalytic converter 7, which may intermittently receive combustion gas from valve 14, and which is pressure and temperature monitored through signal C7, which is fed into said computer. Converter may contain filters and afterburner units and choked by muffler 8. Exhaust gas flows from converter 7 through muffler 8, and from there exhausts through open tailpipe end 9. Muffler 8 or the tailpipe gas may be temperature and alpha monitored by signal C9, which is also fed into said computer. Filter 2, cooler 3 and compressor 4, as well as turbine 6, converter 7 and muffler 8 may however be eliminated. Some of the gas flowing out of valve 52 may be returned to space 56 through valve 51. Such process is called EGR (exhaust gas recycling), which does not interfere with the above specified CGR process. The opening time duration of valves 51 and 52 may overlap, but even that may not ensure the full scavenging of space 56. In that case, some residual exhaust gas may remain in space 56 at the closing of valve 52, which is called residual or inherent EGR. Some portion of the exhaust gas may also be diverted from after leaving turbine 6 to before entering compressor 4. That process is called forced EGR, which reduces the amount of air, which space 56 may receive. Such reduction limits the oxygen available for combustion, and thereby the power, which can be harvested from crankshaft 58.

CGR can be two ways or one way only. In a two way CGR, the combustion gas flows in and out any or all cylinders, while in a one way CGR, it only flows out from one cylinder and flows into another. CGR fluctuates oscillating in the former and flows one way in the letter manifold or CG pipeline. Two-way flow CGR is twice as efficient as the one-way flow CGR. Finally, CGR works at all engine loads, not only at part load, as EGR does and unlike EGR, by heat recycling and retaining, CGR boosts engine efficiency and thereby saves fuel, while EGR does not. CGR allows passing excess air to the catalytic converter, improving its efficiency, even at very high engine loads.

The present invention is described above with reference to a preferred embodiment. However, those skilled in the art will recognize that changes and modifications may be made in the described embodiment without departing from the nature and scope of the present invention. For instance, chocking valves can be added to reduce gas flow in the CGR manifold and the CGR can be configured to be self-regulating without the use of computer control. Such configurations are hereby instructive. Also instructive the heat insulation or cooling said manifold or pressure vessels and their pipe connections.

Various further changes and modifications to the embodiment herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope thereof.

Having fully described the invention in such clear and concise terms as to enable those skilled in the art to understand and practice the same, the invention claimed is: 

1. Manifold coupled to at least one cylinder of a diesel engine through at least one valve to pass or block gas flow between said manifold and said cylinder, with all the following concurrent restrictions imposed on said flow: a) any other gas flow between said cylinder and any other place is blocked, b) outflow out of said cylinder is blocked when the pressure in said cylinder is rising and furthermore when the pressure in said cylinder is higher than in said manifold and furthermore during the larger part of said pressure rising, c) inflow into said cylinder is blocked when the pressure in said cylinder is falling and furthermore when the pressure in said cylinder is lower than in said manifold and furthermore during the larger part of said pressure falling.
 2. Manifold coupled to at least a pair of the cylinders of a multi-cylinder diesel engine through at least one valve to pass or block gas flow between said manifold and said cylinder, with all the following concurrent restrictions imposed on said flow: a) any other gas flow between said cylinder and any other place is blocked, b) outflow out of said cylinder is blocked when the pressure in said cylinder is rising and furthermore when the pressure in said cylinder is higher than in said manifold and furthermore during the larger part of said pressure rising, c) inflow into said cylinder is blocked when the pressure in said cylinder is falling and furthermore when the pressure in said cylinder is lower than in said manifold and furthermore during the larger part of said pressure falling.
 3. Manifold as per claim 1 having means to dump gas when said flow is blocked.
 4. Manifold as per claim 2 having means to dump gas when said flow is blocked.
 5. Manifold as per claim 1, whereas said valve is cam operated.
 6. Manifold as per claim 2, whereas said valve is cam operated.
 7. Manifold as per claim 1, whereas said valve is electronically controlled.
 8. Manifold as per claim 2, whereas said valve is electronically controlled.
 9. Manifold as per claim 1, whereas said valve is an internally piloted pneumatic valve.
 10. Manifold as per claim 1, whereas said valve is an externally piloted pneumatic valve.
 11. Manifold as per claim 1, whereas said valve is a hydraulic valve.
 12. Manifold as per claim 2, whereas said valve is an internally piloted pneumatic valve.
 13. Manifold as per claim 2, whereas said valve is an externally piloted pneumatic valve.
 14. Manifold as per claim 2, whereas said valve is a hydraulic valve. 